Thiadiazole substituted triazines

ABSTRACT

This invention discloses new compounds of the formula   wherein R1 and R2 are each lower alkyl; and R3 is selected from the group consisting of alkyl, alkenyl, cycloalkyl, haloalkyl, and   WHEREIN X is selected from the group consisting of alkyl, alkenyl, halogen, haloalkyl, nitro, alkoxy, alkylthio and dialkylamino; and n is an integer from 0 to 3. Further disclosed are herbicidal compositions utilizing as an essential active ingredient a compound of the above description.

United States Patent [1 1 Krenzer Aug. 5, 1975 THIADIAZOLE SUBSTITUTED TRIAZINES [75] lnventor: John Krenzer, Oak Park, 111.

[73] Assignee: Velsicol Chemical Corporation,

Chicago, Ill.

[22] Filed: Feb. 27, 1974 [21] Appl. No.: 446,566

Related U.S. Application Data [60] Division of Ser. No. 250.092, May 5, 1972, Pat. No. 3,849,412, which is a continuation-in-part of Ser. No. 225.616, Feb. 11, 1972, abandoned.

Primary E.wminerLewis Gotts Assistant E.\'aminerCatherine L. Mills Attorney, Agent, or F irm--Robert J. Schwarz; Dietmar H. Olesch [57] ABSTRACT This invention discloses new compounds of the formula wherein R and R are each lower alkyl; and R is selected from the group consisting of alkyl, alkenyl, cycloalkyl, haloalkyl, and

wherein X is selected from the group consisting of alkyl, alkenyl. halogen, haloalkyl, nitro, alkoxy, alkylthio and dialkylamino; and n is an integer from 0 to 3. Further disclosed'are herbicidal compositions utilizing as an essential active ingredient a compound of the above description;

5 Claims, No Drawings THIADIAZOLE SUBSTITUTED TRIAZINES This application is a divisional of Ser. No. 250,092, filed May 5, 1972, now US. Pat. No. 3,849,412 which is a continuation-in-part of Ser. No. 225,6 1 6, filed Feb. 1 1, 1972, now abandoned.

This invention relates to new chemical compositions of matter and more specifically relates to new compounds of the formula wherein R and R are each lower alkyl and R is selected from the group consisting of alkyl, alkenyl, cycloalkyl, haloalkyl, and

wherein X is selected from the group consisting of lower alkyl, chlorine, bromine, trifluoromethyl, nitro, lower alkoxy, lower alkylthio and di(lower alkyl- )amino; and n is an integer from to 3.

The compounds of the present invention are unexpectedly useful as pesticides particularly as herbicides.

The compounds of the present invention can be readily prepared from a thiadiazole substituted urea of the formula wherein R and R are as heretofore described, by reaction first with aqueous formaldehyde and then with an amine of the formula R2! H-I IH 111 wherein R is as heretofore described. The reaction of the urea of Formula II with the aqueous formaldehyde can be effected by preparing a solution or slurry of the urea in an organic liquid such as dimethylformamide, cooling the solution or slurry to a temperature below about 35C and thereafter adding the aqueous formaldehyde at a concentration of from about 10 to about 40 percent by weight thereto. After the addition of the formaldehyde the reaction mixture can be stirred for a period of about one-half hour if desired. After this time the amine of Formula III can be added to the reaction mixture. The amine can be added as such or in the form of a solution in a suitable solvent. Upon addition of the amine the reaction mixture can be heated at a temperature of from 40 to about C for a period of from /2 to about 8 hours to insure completion of the reaction. After this time the reaction mixture can be stripped of solvents under reduced pressure to yield the desired product as a residue. This residue can be used as such or can be further purified by standard techniques.

The thiadiazole substituted ureas of Formula II when not available can be prepared from an appropriately substituted thiadiazole having the formula S (lV) wherein R is as heretofore described, by reaction with an isocyanate of the formula wherein R is as heretofore described. This reaction can be readily effected by incrementally adding the isocyanate to a solution of the thiadiazole. After the addition is completed the reaction mixture can be heated with stirring to ensure completion of the reaction. After this time the reaction mixture can be stripped of solvent to yield the desired thiadiazole substituted urea.

Exemplary thiadiazole compounds of Formula IV useful for preparing the compounds of the present invention are Z-amin'o-S-methyl-l ,3,4-thiadiazolc, 2- amino-S-ethyl-l ,3,4-thiadiazole, 2-amino-5-isopropyl- 1 ,3,4-thiadiazole, 2-amino-5-t-butyl-l ,3,4-thiadiazole, 2-amino-5-hexyl-l,3,4-thiadiazole, and the like.

Exemplary isocyanates of Formula V are methyl isocyanate, ethyl isocyanate, propyl isocyanate, butyl isocyanate. pentyl isocyanate, hexyl isocyanate and the like.

Exemplary amines of Formula Ill useful for preparing the compounds of this invention are methylamine, ethylamine. propylamine, butylamine, pentylamine, hexylamine, allylamine, pentenylamine, cyclopropylamine, cyclopentylamine, cyclohexylamine, cycloheptylamine, phenylamine, 2-methyl-4-ch1oropheny1amine, 3,4-dibromophenylamine, 4-nitrophenylamine, 4-trifluoromethylphenylamine, Z-methoxyphenylamine, 3-methylthiophenylamine, 2- dimethylaminophenylamine, 4-fluorophenylamine, 3-propyl-S-ethoxyphenylamine, 3-allylphenylamine, 2-pentyl-4-butyloxyphenylamine, 3- dipropylaminophenylamine and the like.

The manner in which the compounds of the present invention can be prepared readily is more specifically illustrated in the following examples.

EXAMPLE 1 EXAMPLE 2 Preparation of 1-(5-1sopropyl-l,3,4-thiadiazol-2-yl)- 3,5-dimethylhexahydro-s-triazine-2-one N-( 5-lsopropyll ,3 ,4-thiadiazol-2-yl )-N -methylurea (1 1.0 grams) was dissolved in dimethylformamide (50 ml) and charged into a glass reaction vessel equipped with a mechanical stirrer and cooling means. The solution is cooled to a temperature below about 35C and aqueous formaldehyde 16 ml; 36% concentration) was incrementally added thereto. The temperature of the reaction mixture was maintained below about 35C during the addition of the formaldehyde. After the addition was completed stirring was continued for a period of about one-half hour. After this time methylamine (8 ml; 40% aqueous solution) was added to the reaction mixture with continued cooling. After the addition was completed the mixture was stirred overnight at room temperature. The reaction mixture was then warmed on a steam bath for a period of about 1 hour and thereafter stripped of solvent under reduced pressure to yield a solid product. This solid product was recrystallized from hexane to yield the desired product 1-( 5-isopropyll ,3,4-thiadiazol-2-yl )-3 .5- dimethylhexahydro-s-triazine-2-onc having a melting point of 67 to 68C.

EXAMPLE 3 Preparation of N-( S-t-Butyl- 1 ,3,4-thiadiazol-2-yl )-N'- methylurea A solution of 2-amino-5-t-butyll ,3,4-thiadiazole (21 grams) in ethyl acetate (120 ml) was charged into a glass reaction vessel equipped with a mechanical stirrer and reflux condenser. Methyl isocyanate (9 grams) was incrementally added to the reaction mixture with stirring. After the addition was completed stirring was continued for an additional period of about one-half hour to ensure completion of the reaction. After this time the reaction mixture was stripped of solvent to yield a solid residue. The residue was washed with hexane to yield the desired product N-(S-t-butyl- 1 ,3,4-thiadiazol- 2-y1)-N' -methylurea. 7

EXAMPLE 4 Preparation of l-( 5-tButyl- 1 ,3,4-thiadiazol-2-yl )-3,5- dimethylhexahydro-s-triazine-2-one N-( S-t-butyl-l ,3,4-thiadiazol-2-yl )-N-methylurea (11.3 grams), dimethylformamide ml) and a solution of formaldehyde (16 ml; 36% concentration) were charged into a glass reaction flask equipped with a mechanical stirrer and reflux condenser. The mixture was stirred for a period of about one-half hour. After this time methylamine (8 ml; 40% aqueous solution) was incrementally added to the reaction mixture over a period of about 30 minutes. The reaction mixture was then stirred at room temperature for a period of about 16 hours. The mixture was thereafter heated on a steam bath for about 2 hours and was then stripped of solvent under reduced pressure to yield a solid residue. This residue was recrystallized from hexane to yield the desired product 1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3,5- dimethylhexahydro-s-triazine-2-one having a melting point of 114 to 116C.

Additional compounds within the scope of the present invention can be prepared by the procedures detailed in the foregoing examples. In the following examples are given the essential starting materials required for preparing the indicated named compounds.

EXAMPLE 5 2-Amino-5-t-butyl-1,3,4-thiadiazole ethyl isocyanate formaldehyde methylamine 1-(5-t-butyl- 1 ,3 ,4-thiadiazol-2-yl)-3-ethyl-5-methylhexahydro-striazine-2-one; m.p. 8688C.

EXAMPLE 6 EXAMPLE 7 2-Amino-5-t-butyl-l,3,4-thiadiazole ethyl isocyanate formaldehyde ethylamine 1-(5-t-buty1- l ,3,4-thiadiazol-2-yl )-3,5-diethylhexahydro-s-triazine- 2-one; m.p. 74-76C.

EXAMPLE 8 2-Amino-5-isopropyll ,3,4-thiadiazole ethyl isocyanate formaldehyde methylamine 1-(5- trifiuoromethyl- 1 ,3,4-thiadiazo1-2-yl )-3-ethyl-5- methylhexahydro-s-triazine-2-one.

EXAMPLE 9 2-Amino-5-pentyl-1 ,3,4-thiadiazole methyl isocyanate formaldehyde ethylamine l-(5- trifluoromethyl- 1 ,3 ,4-thiadiazol-2-yl )-3-methyl-5 ethylhexahydro-s-triazine-Z-one.

EXAMPLE 10 2-Amino-5-methyl-1,3,4-thiadiazole n-butyl isocyanate phenylamine l-(5-methyl-1,3,4-thiadiazol-2- yl)-3-n-butyl-5phenylhexahydro-s-triazine-Z-one.

EXAMPLE 1 1 Z-Amino-S-t-butyl-l ,3,4-thiadiazole n-hexyl isocyanate 2-methyl-4-chlorophenylamine l-(S-t-butyl- 1,3 ,4-thiadiazol-2-yl )-3-n-hexyl-5-( 2-methyl-4- chlorophenyl )hexahydro-s-triazine-Z-one.

EXAMPLE 1 2 2-Amino-5-n-hexyl-1,3,4-thiadiazole methyl isocyanate 2-methoxy-4-isopropylphenylamine l-(5-nhexyl-l ,3 ,4-thiadiazol-2-yl)-3-methyl-5-( 2-methoxy-4- isopropylphenyl)hexahydro-s-triazine-2-one.

Additional compounds within the scope of the present invention which can be prepared by the procedures of the foregoing examples are l-(5-ethyl-l,3,4- thiadiazol-Z-yl )-3-n-propyl-5-( 3-allyl-5- chloromethylphenyl )hexahydro-s-triazine-2-one, l-( 5- methyl-1,3 ,4-thiadiazol-2-yl )-3-methyl-5-nbutylhexahydro-s-triazine-Z-one, l-( S-t-butyl-l ,3 ,4- thiadiazol-Z-yl )-3-methyl-5-n-hexylhexahydro-striazine-Z-one, l-( S-t-butyll ,3,4-thiadiazol-2-yl )-3- methyl-5-trifluoromethylhexahydro-s-triazine-2-one, l-( S-t-butyl-l ,3 ,4-thiadia2ol-2-yl )-3-methyl-5- trichloropropylhexahydro-s-triazine-2-one, l-( 5- isopropyl- I ,3,4-thiadiazol-2-yl)-3-methyl-5-bromo-nhexylhexahydro-s-triazine-2-one, l-( 5-t-butyl-l ,3 ,4- thiadiazol-Z-yl )-3-methyl-5-( 3-n-pentyl-5- nitrophenyl)hexahydro-s-triazine-2-one, l-(5-t-butyl- 1,3 ,4-thiadiazol-2-yl)-3-methyl-5-(2-n-hexyl-4,5- dibromophenyl)hexahydro-s-triazine-2-one, isopropyl- 1 ,3,4-thiadiazol-2-yl)-3-methyl-5-( 2- methylthio-4-dimethylaminophenyl )-hexahydro-striazine-2-one, l-( S-methyll ,3,4-thiadiazol-2-yl )-3- methyl-5-( 2-n-propoxy-4-di-nbutylaminophenyl )hexahydro-s-triazine-2-one, l-( 5-npentyl-l ,3 ,4-thiadiazol- 2-yl )-3-methyl-5-(2-hexyloxy- 4-trifluoromethylphenyl )hexahydro-s-triazine-2-one l-( S-methyll ,3,4-thiadiazol-2-yl)-3-methyl-5-( 2-npropylthio-4-iodophenyl)hexahydro-s-triazine-2-one, l-( S-methyll ,3,4-thiadiazol-2-yl)-3-methyl-5-( 2-nhexylthio-4-fluorophenyl)-hexahydro-s-triazine-2-one, l-( S-methyl-l ,3 ,4-thiadiazol-2-yl )-3-methyl-5-( 3-di-n-' hexylaminophenyl)hexahydro-s-triazine-2 one, l-(5-tbutyll ,3 ,4-thiadiazol-2-yl )-3-methyl-5- cyclopropylhexahydro-s-triazine-2-one, l-(S-t-butyll ,3 ,4-thiadiazol-2-yl )-3-methyl-5-allylhexahydro-striazine-Z-one, l-( S-t-butyll ,3 ,4-thiadiazol-2-yl )-3- methyl-5-cyclopentylhexahydro-s-triazine-2-one, l-( 5- t-butyll ,3,4-thiadiazol-2-yl)-3-methyl-5- cyclohexylhexahydro-s-triazine-Z-one, l,3,4-thiadiazol-2-yl)-3-methyl-5- cycloheptylhexahydro-s-triazine-2-one and the like.

For practical use as herbicides the compounds of this invention are generally incorporated into herbicidal compositions which comprise an inert carrier and a herbicidally toxic amount of such a compound. Such herbicidal compositions, which can also be called formulations, enable the active compound to be applied conveniently to the site of the weed infestation in any desired quantity. These compositions can be solids such as dusts, granules, or wettable powders; or they can be liquids such as solutions, aerosols, or emulsifiable concentrates.

For example, dusts can be prepared by grinding and nating the compound, usually dissolved in a suitable solvent, onto and into granulated carriers such as the attapulgites or the vermiculites, usually of a particle size range of from about 0.3 to 1.5 mm. Wettable powders, which can be dispersed in water or oil to any desired concentration of the active compound, can be prepared by incorporating wetting agents into concentrated dust compositions.

In some cases the active compounds are sufficiently soluble in common organic solvents such as kerosene or xylene so that they can be used directly as solutions in these solvents. Frequently, solutions of herbicides can be dispersed under superatmospheric pressure as aerosols. However, preferred liquid herbicidal compositions are emulsifiable concentrates, which comprise an active coinpound according to this invention and as the inert carrier, a solvent and an emulsifier. Such emulsifiable'concentrates can be extended with water and/or oil to any desired concentration of active compound for application as sprays to the site of the weed infestation. The emulsifiers most commonly used in these concentrates are nonionic or mixtures of nonionic with anionic surface-active agents. With the use of some emulsifier systems an inverted emulsion (water in oil) can be prepared for direct application to weed infestations.

A typical herbicidal composition according to this invention is illustrated by the following example, in which the quantities are in parts by weight.

EXAMPLE 13 Preparation of a Dust The above ingredients are mixed in a mechanical grinder-blender and are ground until a homogeneous, freeflowing dust of the desired particle size is obtained. This dust is suitable for direct application to the site of the weed infestation.

The compounds of this invention can be applied as herbicides in any manner recognized by the art. One method for the control of weeds comprises contacting the locus of said weeds with a herbicidal composition comprising an inert carrier and as an essential active ingredient, in a quantity which is herbicidally toxic to said weeds, a compound of the present invention. The concentration of the new compounds of this invention in the herbicidal compositions will vary greatly with the type of formulation and the purpose for which it is designed, but generally the herbicidal compositions will comprise from about 0.05 to about percent by weight of the active compounds of this invention. In a preferred embodiment of this invention, the herbicidal compositions will comprise from about 5 to about 75 percent by weight of the active compound. The compositions can also comprise such additional substances as other pesticides, such as insecticides, nematocides, fungicides, and the like; stabilizers, spreaders, deactivators, adhesives, stickers, fertilizers, activators, synergists and the like.

The compounds of the present invention are also useful when combined with other herbicides and/or defoliants, dessicants, growth inhibitors and the like in the herbicidal compositions heretofore described. These other materials can comprise from about percent to about 95 percent of the active ingredients in the herbicidal compositions. Use of combinations of these other herbicides and/or defoliants, dessicants, etc. with the compounds of the present invention provide herbicidal compositions which are more effective in controlling weeds and often provide results unattainable with separate compositions of the individual herbicides. The other herbicides, defoliants, dessicants and plant growth inhibitors, with which the compoundsof this invention can be used in the herbicidal compositions to control weeds, can include chlorophenoxy herbicides such'as 2,4-D, 2,4,5-T, MCPA, MCPB, 4(2,4-DB), 2,4- DEB, 4-CPB, 4-CPA, 4-CPP, 2,4,5-TB, 2,4,5-TES, 3,4- DA, silvex and the like; carbamate herbicides such as lPC, ClPC, swep, barban, BCPC, CEPC, CPPC, and the like; thiocarbamate and dithiocarbamate herbicides such as CDEC, metham sodium, EPTC, diallate, PEBC, perbulate, vernolate, and the like; substituted urea herbicidessuch as norea, siduron, dichloral urea, chloroxumn, cycluron, fenuron, monuron, monuron TCA, diuron, linuron, monolinuron, neburon, buturon, trimeturon and the like; symmetrical triazine herbicides such as simazine, chlorazine, atraone, desmetryne, norazine, ipazine, prometryn, atrazine, trietazine, simetone, prometone, propazine, ametryne, and the like; chloroacetamide herbicides such as alpha-chloro-N,N- dimethylacetamide, CDEA, CDAA, alpha-chloro-N- isopropylacetamide, 2-chloro-N-isopropylacetanilide, 4-(chloroacetyl)morpholine, l- (chloroacetyl)piperidine, and the like; chlorinated aliphatic acid herbicides such as TCA, dalapon, 2,3- dichloropropionic acid, 2,2,3-TPA and the like; chlorinated benzoic acid and phenylacetic acid herbicides such as 2,3,6-TBA, 2,3,5,6-TBA, dicamba, tricamba, amiben fenac PB'A, 2-methoxy-3 ,6- dichlorophenylacetic acid, 3-methoxy-2,6- diehlorophenylacetic acid, 2-methoxy-3,5,6-trichlorophenylacetic acid, 2,4-dichloro- 3-nitrobenzoic acid and the like; and such compounds as aminotriazole, maleic hydrazide, pheny] mercuric acetate, endothal, biuret, technical chlordane, dimethyl 2,3,5,6-tetrachloroterephthalate, diquat, erbon, DNC, DNBP, dichlobeniLDPA, diphenamid, dipropalin, trifluralin, solan, dicryl, merphos, DMPA, DSMA, MSMA, potassium azide, acrolein, benefin, bensulide, AMS, bromacil, 2-( 3 ,4-dichlorophenyl)-4-methyl-1 ,2,4- oxadiazolidine-3,5-dione, bromoxynil, cacodylic acid, CMA, CPMF, cypromid, DCB, DCPA, dichlone, diphenatril, DMTT, DNAP, EBEP, EXD, HCA, ioxynil, lPX, isocil, potassium cyanate, MAA, MAMA, MCPES, MCPP, MH, molinate, NPA, OCH, paraquat, PCP, picloram, DPA, PCA, pyrichlor, sesone, terbacil, terbutol, TCBA, brominil, CP-50,144, H-l 76-1 H-732, M-2901, planavin, sodium tetraborate, calcium cyanamid, DEF, ethyl xanthogen disulfide, sindone, sindone B, propanil and the like.

Such herbicides can also be used in the methods and compositions of this invention in the form of their salts, esters, amides, and other derivatives whenever applicable to the particular parent compounds.

Weeds are undesirable plants growing where they are not wanted, having no economic value, and interfering with the production of cultivated crops, with the growing of ornamental plants, or with the welfare of livestock. Many types of weeds are known, including annuals such as pigweed, lambsquarters, foxtail, crabgrass,

wild mustard, field penny-Cress, ryegrass, goose-grass, chickweed, wild oats, velvet leaf, purselane, barnyard grass, smartweed, knotweed, cocklebur, wild buckwheat, kochia, medic, corn cockle, ragweed, sowthistle, coffee-weed, croton, cuphea, dodder, fumitory, groundsel, hemp nettle, knowel, spurge, spurry, emex, jungle rice, pondweed, dog fennel, carpetweed, morning glory, bed-straw, ducksalad and naiad; biennials such as wild carrot, matricaria, wild barley, campion, chamomile, burdock, mullein, roundleaved mallow, bullthistle, hounds-tongue, moth mullein, and purple star thistle; or perennials such as white cockle, perennial rye-grass, quackgrass, Johnson grass, Canada thistle, hedge bindweed, Russian knapweed, mesquite, toadflax, yarrow, aster, gromwell, horsetail, ironweed, sesbania, bulrush, cattail and winter-Cress.

Similarly, such weeds can be classified as broadleaf or grassy weeds. It is economically desirable to control the growth of such weeds without damaging beneficial plants or livestock.

The new compounds of this invention are particularly valuable for weed control because they are toxic to many species and groups of weeds while they are relatively non-toxic to many beneficial plants. The exact amount of compound required will depend on a variety of factors, including the hardiness of the particular weed specied, weather, type of soil, method of application, the king of beneficial plants in the same area, and the like. Thus, while the application of up to only about one or two ounces of active compound per acre may be sufficient for good control of a light infestation of weeds growing under adverse conditions, the application of ten pounds or more of active compound per acre may be required for good control of a dense infestation of hardy perennial weeds growing under favorable conditions.

The herbicidal toxicity of the new compounds of this invention can be illustrated by many of the established testing techniques known to the art, such as preand post-emergence testing.

The herbicidal activity of the compounds of this invention was demonstrated by experiments carried out for the pre-emergence control of a variety of weeds. In these experiments small plastic greenhouse pots filled with dry soil were seeded with the weed seeds. Twentyfour hours or less after seeding the pots were sprayed with water until the soil was wet and the test compounds formulated as aqueous emulsions of acetone solutions containing emulsifiers were sprayed at the indicated concentrations on the surface of the soil.

After spraying, the soil containers were placed in the greenhouse and provided with supplementary heat as required and daily or more frequent watering. The plants were maintained under these conditions for a period of 20 days, at which time the condition of the plants and the degree of injury to the plants was rated on a scale of from O to 10, as follows: 0 no injury, 1,2 slight injury, 3 ,4 moderate injury, 5 ,6 moderately severe injury, 7,8,9 severe injury and 10 death. The effectiveness of these compounds is demonstrated by the following data:

9 TABLE 1 lnjury Rating Prod. of Ex. 4 Rate lbs/acre The herbicidal activity of the compounds of this invention was also demonstrated by experiments carried out for the post-emergence control of a variety of weeds. In these experiments the compounds to be tested were formulated as aqueous emulsions and sprayed at the indicated dosage on the foliage of the weeds that had attained a prescribed size. After spraying, the plants were placed in a greenhouse and watered daily or more frequently. Water was not applied to the foliage of the treated plants. The severity of the injury was determined 13 days after treatment and was rated on the scale of from O to as heretofore described. The effectiveness of these compounds is demonstrated by the following data:

TABLE II Injury Rating I claim:

1. A herbicidal composition comprising an inert carrier and as an essential active ingredient in a quantity 5 toxic to weeds a compound of the formula wherein R and R are each lower alkyl; R is selected from the group consisting of lower alkyl, lower alkenyl, cycloalkyl of from 3, to 7 carbon atoms, lower haloalkyl, and

wherein X is selected from the group consisting of lower alkyl, halogen, trifluoromethyl, nitro, lower alkoxy, lower alkylthio and di(lower alkyl) amino; and n is an integer from O to 3.

2. A method of controlling weeds which comprises contacting said weeds with a herbicidally effective amount of a compound of claim 1.

3. The method of claim 2 wherein the essential active ingredient is l-(S-isopropyl-l,3,4-thiadiazol-2-yl)-3.5-

dimethylhexahydro-s-triazine-2-one.

4. The method of claim 2 wherein the essential active ingredient is l-(S-t-butyl-l,3,4-thiadiazol-2-yl)-3,5- dimethylhexahydro-s-triazine-2-one.

5. The method of claim 2 wherein the essential active ingredient is l-( S-t-butyll ,3 ,4-thiadiazol-2-yl )-3-ethyl- 5-methylhexahydro-s-triazine-2-one. 

1. A HERBICIDAL COMPOSITION COMPRISING AN INERT CARRIER AND AS AN ESSENTIAL ACTIVE INGREDIENT IN A QUANTITY TOXIC TO WEEDS A COMPOUND OF THE FORMULA
 2. A method of controlling weeds which comprises contacting said weeds with a herbicidally effective amount of a compound of claim
 3. The method of claim 2 wherein the essential active ingredient is 1-(5-isopropyl-1,3,4-thiadiazol-2-yl)-3,5-dimethylhexahydro-s-triazine-2 -one.
 4. The method of claim 2 wherein the essential active ingredient is 1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3,5-dimethylhexahydro-s-triazine-2-one.
 5. The method of claim 2 wherein the essential active ingredient is 1-(5-t-butyl-1,3,4-thiadiazol-2-yl)-3-ethyl-5-methylhexahydro-s-triazine-2 -one. 